Removing a colony

Sites used for maternity colonies are essential to the reproduction of bats. Although it is important to preserve them, cohabiting with bats can be difficult. Nevertheless, it is important not to disturb a maternity colony during the breeding period, as young bats that are unable to fly will become trapped inside and die. Their mothers will therefore use any means possible to reach their young. Colonies may be removed in April or May, before the pups are born, or between late September and October, when the colony disperses.

If it is absolutely necessary to remove a colony, you can do so yourself by following these steps:

Step one: Observation

This can be done during the summer. To remove a colony from a building, you must locate the openings to the colony and block them. The most frequently used openings can sometimes be identified by the blackish stains that surround them. Observe the building at dusk to find the location(s) from which the bats emerge.

Step two: Blocking the openings

In October, when the bats have begun their migration, you can start blocking the openings with silicone sealant, steel wool, mortar, a screen, etc. While completing this task, it is important to block all openings used by the bats as well as any other openings measuring 2 cm or more. Leave one or two holes open to ensure that any remaining bats can escape.

Step three: Eviction

Install a screen or polypropylene bird netting in front of the remaining openings. Using staples or small nails, attach the top and sides of the screen/netting to the building. Allow the remaining lower part to hang in front of the opening. Do not attach the bottom. This will allow the remaining bats to exit the building, but they will not be able to re-enter. At the end of October, the remaining openings can be closed off permanently. For more information, consult the following links:

Step four: Installing a bat house

Bats are very loyal to their roosting sites. It is certain that they will return the following spring and attempt to find a way inside, which is why it is important to block all openings. However, it is possible to offer the bats an alternative. Install bat houses as far off the ground as possible to protect the bats from predators. The ideal spot is close to the opening that was most frequently used by the bats. The number and size of bat houses will depend on the size of the colony, but installing several houses is recommended to maximize the chances of success.